They didn't put SBF on trial for campaign finance because they already got him. I don't understand why people are reaching for conspiracy theories here.
Also there's a mechanism for taking into account charges like the campaign finance violations during his sentencing. (Which I'm not sure how I feel about)
And in general his sentencing was about whether they were going to put him away for a defacto life sentence or not. And I'm not sure that more charges for the same crime spree would affect that.
You only get fire risks when the things they touch are themselves tiny (like dust), so they're unable to absorb and spread the heat.
A similar thing happens when you bake with tinfoil. The foil will be at like 350 F, but you can still touch it basically immediately if you're willing to gamble that nothing with thermal mass is stuck to it where you can't see. It just doesn't have enough thermal mass on its own to burn you, but if there's a good-sized glob of cheese or water or something on the other side you can really be in for a nasty surprise.